Method for improving engine fuel efficiency

ABSTRACT

A method for improving fuel efficiency, while maintaining or improving wear protection, in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil having a HTHS viscosity of less than 2.6 cP at 150° C. In one form, the formulated oil has a composition that includes a lubricating oil base stock as a major component, and zinc dialkyl dithio phosphate, a mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents; and a viscosity index improver, as minor components. The lubricating oil has a HTHS viscosity of less than 2.6 cP at 150° C. The composition contains less than 2 weight percent of the viscosity index improver, based on the total weight of the formulated oil or lubricating engine oil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 61/559,294, filed on Nov. 14, 2011; which is incorporated herein inits entirety by reference.

FIELD

This disclosure relates to lubricating engines using formulatedlubricating oils to improve engine fuel efficiency without sacrificingengine durability.

BACKGROUND

Fuel efficiency requirements for passenger vehicles are becomingincreasingly more stringent. New legislation in the United States andEuropean Union within the past few years has set fuel economy andemissions targets not readily achievable with today's vehicle andlubricant technology. In order to improve lubricant fuel economyperformance, reduction of viscosity is typically the best path; however,present day lubricant oils with a HTHS (ASTM D4683) viscosity of lessthan 2.6 cP at 150° C. would not be expected to be able to provideacceptable passenger vehicle engine durability performance.

HTHS is the measure of a lubricant's viscosity under conditions thatsimulate severe engine operation. Under high temperatures and highstress conditions, viscosity index improver degradation can occur. Asthis happens, the viscosity of the oil decreases which may lead toincreased engine wear.

A viscosity index improver is typically added to engine oil in order toprovide appropriate viscosity at high and low temperatures and therebywiden the application temperature range. High molecular weight polymersare widely used as viscosity index improvers. The high molecular weightpolymer-based viscosity index improver has the typical property of suchimprovers; that is, a temporary viscosity decrease due to orientation,etc., occurs during operation at high speed/high load or under otherhigh shear conditions, and irreversible viscosity decrease occurs due tomolecular weight decrease as a result of chopping of the polymermolecules when the shear conditions become severe. Also, when theviscosity of the engine oil is reduced, the engine oil film itselfbecomes thinner, and the opportunity for increased engine wear arises.Therefore, for engine oils in which a viscosity index improver is added,if the viscosity is reduced by simply reducing the viscosity of the baseoil, it is not possible to guarantee the oil film under high shearconditions, and engine wear can easily occur.

Despite the advances in lubricant oil formulation technology, thereexists a need for an engine oil lubricant that effectively improves fueleconomy while providing superior antiwear performance, and has thecapability to do so through reduction or removal of viscosity indeximprovers.

SUMMARY

This disclosure relates in part to a method for improving fuelefficiency, while maintaining or improving wear protection, in an enginelubricated with a lubricating oil by reducing the amount of a viscosityindex improver in the lubricating oil sufficient for the lubricating oilto have a HTHS viscosity of less than 2.6 cP at 150° C.

This disclosure also relates in part to a method for improving fuelefficiency, while maintaining or improving wear protection, in an enginelubricated with a lubricating oil by using as the lubricating oil aformulated oil having a HTHS viscosity of less than 2.6 cP at 150° C.The formulated oil has a composition that comprises a lubricating oilbase stock as a major component, and zinc dialkyl dithio phosphate, amixture of (i) at least two alkali metal detergents, (ii) at least twoalkaline earth metal detergents, or (iii) one or more alkali metaldetergents and one or more alkaline earth metal detergents; and aviscosity index improver, as minor components. The composition containsless than 2 weight percent of the viscosity index improver, based on thetotal weight of the formulated oil. The composition is sufficient forthe formulated oil to pass wear protection requirements of one or moreengine tests selected from TU3M, Sequence IIIG, Sequence IVA andOM646LA.

This disclosure further relates in part to a lubricating engine oilhaving a composition comprising a lubricating oil base stock as a majorcomponent, and a zinc dialkyl dithio phosphate, a mixture of (i) atleast two alkali metal detergents, (ii) at least two alkaline earthmetal detergents, or (iii) one or more alkali metal detergents and oneor more alkaline earth metal detergents, e.g., magnesium sulfonate andcalcium salicylate; and a viscosity index improver, as minor components.The lubricating engine oil has a HTHS viscosity of less than 2.6 cP at150° C. The composition contains less than 2 weight percent of theviscosity index improver, based on the total weight of the lubricatingengine oil. The composition is sufficient for the lubricating engine oilto pass wear protection requirements of one or more engine testsselected from TU3M, Sequence IIIG, Sequence IVA and OM646LA.

This disclosure yet further relates in part to a method for improvingfuel efficiency, while maintaining or improving wear protection, in anengine lubricated with a lubricating oil by using as the lubricating oila formulated oil having a HTHS viscosity of less than 2.6 cP at 150° C.The formulated oil has a composition that comprises a lubricating oilbase stock as a major component, and zinc dialkyl dithio phosphate, anda mixture of (i) at least two alkali metal detergents, (ii) at least twoalkaline earth metal detergents, or (iii) one or more alkali metaldetergents and one or more alkaline earth metal detergents, as minorcomponents. The composition can optionally contain a viscosity indeximprover in an amount less than 2 weight percent, based on the totalweight of the formulated oil. The composition is sufficient for theformulated oil to pass wear protection requirements of one or moreengine tests selected from TU3M, Sequence IIIG, Sequence IVA andOM646LA.

This disclosure also relates in part to a lubricating engine oil havinga composition comprising a lubricating oil base stock as a majorcomponent, and a zinc dialkyl dithio phosphate, and a mixture of (i) atleast two alkali metal detergents, (ii) at least two alkaline earthmetal detergents, or (iii) one or more alkali metal detergents and oneor more alkaline earth metal detergents, e.g., magnesium sulfonate andcalcium salicylate, as minor components. The lubricating engine oil hasa HTHS viscosity of less than 2.6 cP at 150° C. The composition canoptionally contain a viscosity index improver in an amount less than 2weight percent, based on the total weight of the formulated oil. Thecomposition is sufficient for the formulated oil to pass wear protectionrequirements of one or more engine tests selected from TU3M, SequenceIIIG, Sequence IVA and OM646LA.

In accordance with this disclosure, improvements in fuel economy areobtained without sacrificing engine durability by a reduction of HTHSviscosity to a level less than 2.6 cP through reduction or removal ofviscosity modifiers. Engine wear protection is maintained even when aviscosity modifier is reduced or removed from the engine oilformulation, leading to substantially lower HTHS viscosities, e.g., 2.6cP or lower at 150° C.

Other objects and advantages of the present disclosure will becomeapparent from the detailed description that follows.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art.

It has now been found that improved fuel efficiency can be attained,while wear protection is maintained or improved, in an engine lubricatedwith a lubricating oil by using as the lubricating oil a formulated oilhaving a HTHS viscosity of less than 2.6 cP at 150° C. The formulatedoil comprises a lubricating oil base stock as a major component, a zincdialkyl dithio phosphate, and a mixture of (i) at least two alkali metaldetergents, (ii) at least two alkaline earth metal detergents, or (iii)one or more alkali metal detergents and one or more alkaline earth metaldetergents; and a viscosity index improver, as minor components. Thelubricating oils of this disclosure are particularly advantageous aspassenger vehicle engine oil (PVEO) products.

The lubricating oils of this disclosure provide excellent engineprotection including anti-wear performance. This benefit has beendemonstrated for the lubricating oils of this disclosure in the SequenceIIIG/IIIGA (ASTM D7320), Sequence IVA (ASTM D6891), PSA TU3MS (CECL-038-94), MB OM646LA (CEC L-099-08), and Caterpillar 1M-PC (ASTM D6618)engine tests at HTHS viscosities less than 2.6 cP (at 150° C.). Thelubricating oils of this disclosure provide improved fuel efficiency. Alower HTHS viscosity engine oil generally provides superior fuel economyto a higher HTHS viscosity product. This benefit has been demonstratedfor the lubricating oils of this disclosure in the MB M111 Fuel Economy(CEC L-054-96) and Sequence VID Fuel to Economy (ASTM D7589) enginetests. By providing outstanding engine protection at very low HTHSviscosities, this disclosure provides improved fuel economy withoutsacrificing engine durability.

The engine lubricating oil of the present disclosure has a HTHSviscosity of less than 2.6 cP at 150° C., preferably less than 2.4 cP at150° C., and more preferably less than 2.2 cP at 150° C.

The lubricating engine oils of this disclosure have a compositionsufficient to pass wear protection requirements of one or more enginetests selected from TU3M, Sequence IIIG, Sequence IVA, OM646LA andothers.

Lubricating Oil Base Stocks

A wide range of lubricating base oils is known in the art. Lubricatingbase oils that are useful in the present disclosure are both naturaloils, and synthetic oils, and unconventional oils (or mixtures thereof)can be used unrefined, refined, or rerefined (the latter is also knownas reclaimed or reprocessed oil). Unrefined oils are those obtaineddirectly from a natural or synthetic source and used without addedpurification. These include shale oil obtained directly from retortingoperations, petroleum oil obtained directly from primary distillation,and ester oil obtained directly from an esterification process. Refinedoils are similar to the oils discussed for unrefined oils except refinedoils are subjected to one or more purification steps to improve at leastone lubricating oil property. One skilled in the art is familiar withmany purification processes. These processes include solvent extraction,secondary distillation, acid extraction, base extraction, filtration,and percolation. Rerefined oils are obtained by processes analogous torefined oils but using an oil that has been previously used as a feedstock.

Groups I, II, III, IV and V are broad base oil stock categoriesdeveloped and defined by the American Petroleum institute (APIPublication 1509; www.API.org) to create guidelines for lubricant baseoils. Group I base stocks have a viscosity index of between 80 to 120and contain greater than 0.03% sulfur and/or less than 90% saturates.Group II base stocks have a viscosity index of between 80 to 120, andcontain less than or equal to 0.03% sulfur and greater than or equal to90% saturates. Group III stocks have a viscosity index greater than 120and contain less than or equal to 0.03% sulfur and greater than 90%saturates. Group IV includes polyalphaolefins (PAO). Group V base stockincludes base stocks not included in Groups I-IV. The table belowsummarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90and/or >0.03% and ≧80 and <120 Group II ≧90 and ≦0.03% and ≧80 and <120Group III ≧90 and ≦0.03% and ≧120 Group IV Includes polyalphaolefins(PAO) and GTL products Group V All other base oil stocks not included inGroups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lardoil, for example), and mineral oils. Animal and vegetable oilspossessing favorable thermal oxidative stability can be used. Of thenatural oils, mineral oils are preferred. Mineral oils vary widely as totheir crude source, for example, as to whether they are paraffinic,naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal orshale are also useful. Natural oils vary also as to the method used fortheir production and purification, for example, their distillation rangeand whether they are straight run or cracked, hydrorefined, or solventextracted.

Group II and/or Group III hydroprocessed or hydrocracked basestocks,including synthetic oils such as polyalphaolefins, alkyl aromatics andsynthetic esters are also well known basestock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oilssuch as polymerized and interpolymerized olefins (polybutylenes,polypropylenes, propylene isobutylene copolymers, ethylene-olefincopolymers, and ethylene-alphaolefin copolymers, for example).Polyalphaolefin (PAO) oil base stocks are commonly used synthetichydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄olefins or mixtures thereof may be utilized. See U.S. Pat. Nos.4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are knownmaterials and generally available on a major commercial scale fromsuppliers such as ExxonMobil Chemical Company, Chevron Phillips ChemicalCompany, BP, and others, typically vary from 250 to 3,000, althoughPAO's may be made in viscosities up to 100 cSt (100° C.). The PAOs aretypically comprised of relatively low molecular weight hydrogenatedpolymers or oligomers of alphaolefins which include, but are not limitedto, C₂ to C₃₂ alphaolefins with the C₈ to C₁₆ alphaolefins, such as1-octene, 1-decene, 1-dodecene and the like, being preferred. Thepreferred polyalphaolefins are poly-1-octene, poly-1-decene andpoly-1-dodecene and mixtures thereof and mixed olefin-derivedpolyolefins. However, the dimers of higher olefins in the range of C₁₄to C₁₈ may be used to provide low viscosity basestocks of acceptably lowvolatility. Depending on the viscosity grade and the starting oligomer,the PAOs may be predominantly trimers and tetramers of the startingolefins, with minor amounts of the higher oligomers, having a viscosityrange of 1.5 to 12 cSt.

The PAO fluids may be conveniently made by the polymerization of analphaolefin in the presence of a polymerization catalyst such as theFriedel-Crafts catalysts including, for example, aluminum trichloride,boron trifluoride or complexes of boron trifluoride with water, alcoholssuch as ethanol, propanol or butanol, carboxylic acids or esters such asethyl acetate or ethyl propionate. For example the methods disclosed byU.S. Pat. No. 4,149,178 or 3,382,291 may be conveniently used herein.Other descriptions of PAO synthesis are found in the following U.S. Pat.Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930; 4,367,352; 4,413,156;4,434,408; 4,910,355; 4,956,122; and 5,068,487. The dimers of the C₁₄ toC₁₈ olefins are described in U.S. Pat. No. 4,218,330.

The hydrocarbyl aromatics can be used as base oil or base oil componentand can be any hydrocarbyl molecule that contains at least 5% of itsweight derived from an aromatic moiety such as a benzenoid moiety ornaphthenoid moiety, or their derivatives. These hydrocarbyl aromaticsinclude alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkylnaphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylatedthiodiphenol, and the like. The aromatic can be mono-alkylated,dialkylated, polyalkylated, and the like. The aromatic can be mono- orpoly-functionalized. The hydrocarbyl groups can also be comprised ofmixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups,cycloalkenyl groups and other related hydrocarbyl groups. Thehydrocarbyl groups can range from C₆ up to C₆₀ with a range of C₈ to C₂₀often being preferred. A mixture of hydrocarbyl groups is oftenpreferred, and up to three such substituents may be present. Thehydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogencontaining substituents. The aromatic group can also be derived fromnatural (petroleum) sources, provided at least 5% of the molecule iscomprised of an above-type aromatic moiety. Viscosities at 100° C. ofapproximately 3 cSt to 50 cSt are preferred, with viscosities ofapproximately 3.4 cSt to 20 cSt often being more preferred for thehydrocarbyl aromatic component. In one embodiment, an alkyl naphthalenewhere the alkyl group is primarily comprised of 1-hexadecene is used.Other alkylates of aromatics can be advantageously used. Naphthalene ormethyl naphthalene, for example, can be alkylated with olefins such asoctene, decene, dodecene, tetradecene or higher, mixtures of similarolefins, and the like. Useful concentrations of hydrocarbyl aromatic ina lubricant oil composition can be 2% to 25%, preferably 4% to 20%, andmore preferably 4% to 15%, depending on the application.

Esters comprise a useful base stock. Additive solvency and sealcompatibility characteristics may be secured by the use of esters suchas the esters of dibasic acids with monoalkanols and the polyol estersof monocarboxylic acids. Esters of the former type include, for example,the esters of dicarboxylic acids such as phthalic acid, succinic acid,alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid,suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic aciddimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc.,with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecylalcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types ofesters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexylfumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate,dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained byreacting one or more polyhydric alcohols, preferably the hinderedpolyols (such as the neopentyl polyols, e.g., neopentyl glycol,trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylolpropane, pentaerythritol and dipentaerythritol) with alkanoic acidscontaining at least 4 carbon atoms, preferably C₅ to C₃₀ acids such assaturated straight chain fatty acids including caprylic acid, capricacid, lauric acid, myristic acid, palmitic acid, stearic acid, arachicacid, and behenic acid, or the corresponding branched chain fatty acidsor unsaturated fatty acids such as oleic acid, or mixtures of any ofthese materials.

Suitable synthetic ester components include the esters of trimethylolpropane, trimethylol butane, trimethylol ethane, pentaerythritol and/ordipentaerythritol with one or more monocarboxylic acids containing from5 to 10 carbon atoms. These esters are widely available commercially,for example, the Mobil P-41 and P-51 esters of ExxonMobil ChemicalCompany).

Other useful fluids of lubricating viscosity include non-conventional orunconventional base stocks that have been processed, preferablycatalytically, or synthesized to provide high performance lubricationcharacteristics.

Non-conventional or unconventional base stocks/base oils include one ormore of a mixture of base stock(s) derived from one or moreGas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate basestock(s) derived from natural wax or waxy feeds, mineral and ornon-mineral oil waxy feed stocks such as slack waxes, natural waxes, andwaxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxyraffinate, hydrocrackate, thermal crackates, or other mineral, mineraloil, or even non-petroleum oil derived waxy materials such as waxymaterials received from coal liquefaction or shale oil, and mixtures ofsuch base stocks.

GTL materials are materials that are derived via one or more synthesis,combination, transformation, rearrangement, and/ordegradation/deconstructive processes from gaseous carbon-containingcompounds, hydrogen-containing compounds and/or elements as feed stockssuch as hydrogen, carbon dioxide, carbon monoxide, water, methane,ethane, ethylene, acetylene, propane, propylene, propyne, butane,butylenes, and butynes. GTL base stocks and/or base oils are GTLmaterials of lubricating viscosity that are generally derived fromhydrocarbons; for example, waxy synthesized hydrocarbons, that arethemselves derived from simpler gaseous carbon-containing compounds,hydrogen-containing compounds and/or elements as feed stocks. GTL basestock(s) and/or base oil(s) include oils boiling in the lube oil boilingrange (1) separated/fractionated from synthesized GTL materials such as,for example, by distillation and subsequently subjected to a final waxprocessing step which involves either or both of a catalytic dewaxingprocess, or a solvent dewaxing process, to produce lube oils ofreduced/low pour point; (2) synthesized wax isomerates, comprising, forexample, hydrodewaxed or hydroisomerized cat and/or solvent dewaxedsynthesized wax or waxy hydrocarbons; (3) hydrodewaxed orhydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T)material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possibleanalogous oxygenates); preferably hydrodewaxed orhydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxyhydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (orsolvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials,especially, hydrodewaxed or hydroisomerized/followed by cat and/orsolvent dewaxed wax or waxy feed, preferably F-T material derived basestock(s) and/or base oil(s), are characterized typically as havingkinematic viscosities at 100° C. of from 2 mm²/s to 50 mm²/s (ASTMD445). They are further characterized typically as having pour points of−5° C. to −40° C. or lower (ASTM D97). They are also characterizedtypically as having viscosity indices of 80 to 140 or greater (ASTMD2270).

In addition, the GTL base stock(s) and/or base oil(s) are typicallyhighly paraffinic (>90% saturates), and may contain mixtures ofmonocycloparaffins and multicycloparaffins in combination withnon-cyclic isoparaffins. The ratio of the naphthenic (i.e.,cycloparaffin) content in such combinations varies with the catalyst andtemperature used. Further, GTL base stock(s) and/or base oil(s)typically have very low sulfur and nitrogen content, generallycontaining less than 10 ppm, and more typically less than 5 ppm of eachof these elements. The sulfur and nitrogen content of GTL base stock(s)and/or base oil(s) obtained from F-T material, especially F-T wax, isessentially nil. In addition, the absence of phosphorous and aromaticsmake this materially especially suitable for the formulation of low SAPproducts.

The term GTL base stock and/or base oil and/or wax isomerate base stockand/or base oil is to be understood as embracing individual fractions ofsuch materials of wide viscosity range as recovered in the productionprocess, mixtures of two or more of such fractions, as well as mixturesof one or two or more low viscosity fractions with one, two or morehigher viscosity fractions to produce a blend wherein the blend exhibitsa target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s)is/are derived is preferably an F-T material (i.e., hydrocarbons, waxyhydrocarbons, wax).

In addition, the GTL base stock(s) and/or base oil(s) are typicallyhighly paraffinic (>90% saturates), and may contain mixtures ofmonocycloparaffins and multicycloparaffins in combination withnon-cyclic isoparaffins. The ratio of the naphthenic (i.e.,cycloparaffin) content in such combinations varies with the catalyst andtemperature used. Further, GTL base stock(s) and/or base oil(s) andhydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed basestock(s) and/or base oil(s) typically have very low sulfur and nitrogencontent, generally containing less than 10 ppm, and more typically lessthan 5 ppm of each of these elements. The sulfur and nitrogen content ofGTL base stock(s) and/or base oil(s) obtained from F-T material,especially F-T wax, is essentially nil. In addition, the absence ofphosphorous and aromatics make this material especially suitable for theformulation of low sulfur, sulfated ash, and phosphorus (low SAP)products.

Base oils for use in the formulated lubricating oils useful in thepresent disclosure are any of the variety of oils corresponding to APIGroup I, Group II, Group III, Group IV, and Group V oils and mixturesthereof, preferably API Group II, Group III, Group IV, and Group V oilsand mixtures thereof, more preferably the Group III to Group V base oilsdue to their exceptional volatility, stability, viscometric andcleanliness features. Minor quantities of Group I stock, such as theamount used to dilute additives for blending into formulated lube oilproducts, can be tolerated but should be kept to a minimum, i.e. amountsonly associated with their use as diluent/carrier oil for additives usedon an “as-received” basis. Even in regard to the Group II stocks, it ispreferred that the Group II stock be in the higher quality rangeassociated with that stock, i.e. a Group II stock having a viscosityindex in the range 100<VI<120.

The base oil constitutes the major component of the engine oil lubricantcomposition of the present disclosure and typically is present in anamount ranging from 50 to 99 weight percent, preferably from 70 to 95weight percent, and more preferably from 85 to 95 weight percent, basedon the total weight of the composition. The base oil may be selectedfrom any of the synthetic or natural oils typically used as crankcaselubricating oils for spark-ignited and compression-ignited engines. Thebase oil conveniently has a kinematic viscosity, according to ASTMstandards, of 2.5 cSt to 12 cSt (or mm²/s) at 100° C. and preferably of2.5 cSt to 9 cSt (or mm²/s) at 100° C. Mixtures of synthetic and naturalbase oils may be used if desired.

Antiwear Additive

A metal alkylthiophosphate and more particularly a metal dialkyl dithiophosphate in which the metal constituent is zinc, or zinc dialkyl dithiophosphate (ZDDP) is an essential component of the lubricating oils ofthis disclosure. ZDDP can be primary, secondary or mixtures thereof.ZDDP compounds generally are of the formula Zn[SP(S)(OR¹)(OR²)]₂ whereR¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. Thesealkyl groups may be straight chain or branched.

Preferable zinc dithiophosphates which are commercially availableinclude secondary zinc dithiophosphates such as those available from forexample, The Lubrizol Corporation under the trade designations “LZ677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite underthe trade designation “OLOA 262” and from for example Afton Chemicalunder the trade designation “HITEC 7169”.

The ZDDP is typically used in amounts of from 0.4 weight percent to 1.2weight percent, preferably from 0.5 weight percent to 1.0 weightpercent, and more preferably from 0.6 weight percent to 0.8 weightpercent, based on the total weight of the lubricating oil, although moreor less can often be used advantageously. Preferably, the ZDDP is asecondary ZDDP and present in an amount of from 0.6 to 1.0 weightpercent of the total weight of the lubricating oil.

Detergent Mixture Additive

A detergent mixture containing (i) at least two alkali metal detergents,(ii) at least two alkaline earth metal detergents, or (iii) one or morealkali metal detergents and one or more alkaline earth metal detergents,is an essential component in the lubricating oils of this disclosure. Atypical detergent is an anionic material that contains a long chainhydrophobic portion of the molecule and a smaller anionic or oleophobichydrophilic portion of the molecule. The anionic portion of thedetergent is typically derived from an organic acid such as a sulfuracid, carboxylic acid, phosphorous acid, phenol, or mixtures thereof.The counterion is typically an alkaline earth or alkali metal.

Salts that contain a substantially stoichiometric amount of the metalare described as neutral salts and have a total base number (TBN, asmeasured by ASTM D2896) of from 0 to 80. Many compositions areoverbased, containing large amounts of a metal base that is achieved byreacting an excess of a metal compound (a metal hydroxide or oxide, forexample) rich an acidic gas (such as carbon dioxide). Useful detergentscan be neutral, mildly overbased, or highly overbased.

It is desirable for at least some detergent used in the detergentmixture to be overbased. Overbased detergents help neutralize acidicimpurities produced by the combustion process and become entrapped inthe oil. Typically, the overbased material has a ratio of metallic ionto anionic portion of the detergent of 1.05:1 to 50:1 on an equivalentbasis. More preferably, the ratio is from 4:1 to 25:1. The resultingdetergent is an overbased detergent that will typically have a TBN of150 or higher, often 250 to 450 or more. Preferably, the overbasingcation is sodium, calcium, or magnesium. A mixture of detergents ofdiffering TBN can be used in the present disclosure.

Preferred detergent mixtures include at least two of the alkali oralkaline earth metal salts of sulfonates, phenates, carboxylates,phosphates, and salicylates, e.g., a mixture of magnesium sulfonate andcalcium salicylate.

Sulfonates may be prepared from sulfonic acids that are typicallyobtained by sulfonation of alkyl substituted aromatic hydrocarbons.Hydrocarbon examples include those obtained by alkylating benzene,toluene, xylene, naphthalene, biphenyl and their halogenated derivatives(chlorobenzme, chlorotoluene, and chloronaphthalene, for example). Thealkylating agents typically have 3 to 70 carbon atoms. The alkarylsulfonates typically contain 9 to 80 carbon or more carbon atoms, moretypically from 16 to 60 carbon atoms.

Alkaline earth phenates are another useful class of detergent. Thesedetergents can be made by reacting alkaline earth metal hydroxide oroxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with analkyl phenol or sulfurized alkylphenol. Useful alkyl groups includestraight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀.Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol,nonylphenol, dodecyl phenol, and the like. It should be noted thatstarting alkylphenols may contain more than one alkyl substituent thatare each independently straight chain or branched. When a non-sulfurizedalkylphenol is used, the sulfurized product may be obtained by methodswell known in the art. These methods include heating a mixture ofalkylphenol and sulfurizing agent (including elemental sulfur, sulfurhalides such as sulfur dichloride, and the like) and then reacting thesulfurized phenol with an alkaline earth metal base.

Metal salts of carboxylic acids are also useful as detergents. Thesecarboxylic acid detergents may be prepared by reacting a basic metalcompound with at least one carboxylic acid and removing free water fromthe reaction product. These compounds may be overbased to produce thedesired TBN level. Detergents made from salicylic acid are one preferredclass of detergents derived from carboxylic acids. Useful salicylatesinclude long chain alkyl salicylates. One useful family of compositionsis of the formula

where R is an alkyl group having 1 to 30 carbon atoms, n is an integerfrom 1 to 4, and M is an alkaline earth metal. Preferred R groups arealkyl chains of at least C₁₁, preferably C₁₃ or greater. R may beoptionally substituted with substituents that do not interfere with thedetergent's function, M is preferably, calcium, magnesium, or barium.More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols bythe Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of thehydrocarbyl-substituted salicylic acids may be prepared by doubledecomposition of a metal salt in a polar solvent such as water oralcohol.

Alkaline earth metal phosphates are also used as detergents and areknown in the art.

Detergents may be simple detergents or what is known as hybrid orcomplex detergents. The latter detergents can provide the properties oftwo detergents without the need to blend separate materials. See U.S.Pat. No. 6,034,039.

Preferred detergent mixtures include at least two of calcium phenates,calcium sulfonates, calcium salicylates, magnesium phenates, magnesiumsulfonates, magnesium salicylates and other related components(including borated detergents) in any combination. A preferred detergentmixture includes magnesium sulfonate and calcium salicylate.

The detergent mixture concentration in the lubricating oils of thisdisclosure can range from 1.0 to 6.0 weight percent, preferably 2.0 to5.0 weight percent, and more preferably from 2.0 weight percent to 4.0weight percent, based on the total weight of the lubricating oil.

Other Additives

The formulated lubricating oil useful in the present disclosure mayadditionally contain one or more of the other commonly used lubricatingoil performance additives including but not limited to dispersants,other detergents, corrosion inhibitors, rust inhibitors, metaldeactivators, other anti-wear agents and/or extreme pressure additives,anti-seizure agents, wax modifiers, viscosity index improvers, viscositymodifiers, fluid-loss additives, seal compatibility agents, frictionmodifiers, lubricity agents, anti-staining agents, chromophoric agents,defoamants, demulsifiers, emulsifiers, densifiers, wetting agents,gelling agents, tackiness agents, colorants, and others. For a review ofmany commonly used additives, see Klamann in Lubricants and RelatedProducts, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0.Reference is also made to “Lubricant Additives” by M. W. Ranney,published by Noyes Data Corporation of Parkridge, N.J. (1973).

The types and quantities of performance additives used in combinationwith the instant disclosure in lubricant compositions are not limited bythe examples shown herein as illustrations.

Dispersants

During engine operation, oil-insoluble oxidation byproducts areproduced. Dispersants help keep these byproducts in solution, thusdiminishing their deposition on metal surfaces. Dispersants used in theformulation of the lubricating oil may be ashless or ash-forming innature. Preferably, the dispersant is ashless. So-called ashlessdispersants are organic materials that form substantially no ash uponcombustion. For example, non-metal-containing or borated metal-freedispersants are considered ashless. In contrast, metal-containingdetergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to arelatively high molecular weight hydrocarbon chain. The polar grouptypically contains at least one element of nitrogen, oxygen, orphosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

Chemically, many dispersants may be characterized as phenates,sulfonates, sulfurized phenates, salicylates, naphthenates, stearates,carbamates, thiocarbamates, phosphorus derivatives. A particularlyuseful class of dispersants are the alkenylsuccinic derivatives,typically produced by the reaction of a long chain hydrocarbylsubstituted succinic compound, usually a hydrocarbyl substitutedsuccinic anhydride, with a polyhydroxy or polyamino compound. The longchain hydrocarbyl group constituting the oleophilic portion of themolecule which confers solubility in the oil, is normally apolyisobutylene group. Many examples of this type of dispersant are wellknown commercially and in the literature. Exemplary U.S. patentsdescribing such dispersants are U.S. Pat. Nos. 3,172,892; 3,215,707;3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012;3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersantare described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025;3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574;3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250;3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. Afurther description of dispersants may be found, for example, inEuropean Patent Application No, 471 071, to which reference is made forthis purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substitutedsuccinic anhydride derivatives are useful dispersants. In particular,succinimide, succinate esters, or succinate ester amides prepared by thereaction of a hydrocarbon-substituted succinic acid compound preferablyhaving at least 50 carbon atoms in the hydrocarbon substituent, with atleast one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between hydrocarbylsubstituted succinic anhydrides and amines. Molar ratios can varydepending on the polyamine. For example, the molar ratio of hydrocarbylsubstituted succinic anhydride to TEPA can vary from 1:1 to 5:1.Representative examples are shown in U.S. Pat. Nos. 3,087,936;3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800;and Canada Patent No. 1,094,044.

Succinate esters are formed by the condensation reaction betweenhydrocarbyl substituted succinic anhydrides and alcohols or polyols.Molar ratios can vary depending on the alcohol or polyol used. Forexample, the condensation product of a hydrocarbyl substituted succinicanhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction betweenhydrocarbyl substituted succinic anhydrides and alkanol amines. Forexample, suitable alkanol amines include ethoxylatedpolyalkylpolyamines, propoxylated polyalkylpolyamines andpolyalkenylpolyamines such as polyethylene polyamines. One example ispropoxylated hexamethylenediamine. Representative examples are shown inU.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydridesused in the preceding paragraphs will typically range between 800 and2,500. The above products can be post-reacted with various reagents suchas sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid.The above products can also be post reacted with boron compounds such asboric acid, borate esters or highly borated dispersants, to form borateddispersants generally having from 0.1 to 5 moles of boron per mole ofdispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols,formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which isincorporated herein by reference. Process aids and catalysts, such asoleic acid and sulfonic acids, can also be part of the reaction mixture.Molecular weights of the alkylphenols range from 800 to 2,500.Representative examples are shown in U.S. Pat. Nos. 3,697,574;3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannichcondensation products useful in this disclosure can be prepared fromhigh molecular weight alkyl-substituted hydroxyaromatics or HN(R)₂group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are wellknown to one skilled in the art; see, for example, U.S. Pat. Nos.3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Preferred dispersants include borated and non-borated succinimides,including those derivatives from mono-succinimides, bis-succinimides,and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbylsuccinimide is derived from a hydrocarbylene group such aspolyisobutylene having a Mn of from 500 to 5000 or a mixture of suchhydrocarbylene groups. Other preferred dispersants include succinicacid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts,their capped derivatives, and other related components. Such additivesmay be used in an amount of 0.1 to 20 weight percent, preferably 0.5 to8 weight percent.

Antioxidants

Antioxidants retard the oxidative degradation of base oils duringservice. Such degradation may result in deposits on metal surfaces, thepresence of sludge, or a viscosity increase in the lubricant. Oneskilled in the art knows a wide variety of oxidation inhibitors that areuseful in lubricating oil compositions. See, Klamann in Lubricants andRelated Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197,for example.

Useful antioxidants include hindered phenols. These phenolicantioxidants may be ashless (metal-free) phenolic compounds or neutralor basic metal salts of certain phenolic compounds. Typical phenolicantioxidant compounds are the hindered phenolics which are the oneswhich contain a sterically hindered hydroxyl group, and these includethose derivatives of dihydroxy aryl compounds in which the hydroxylgroups are in the o- or p-position to each other. Typical phenolicantioxidants include the hindered phenols substituted with C₆+ alkylgroups and the alkylene coupled derivatives of these hindered phenols.Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol;2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol;2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol;2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecylphenol. Other useful hindered mono-phenolic antioxidants may include forexample hindered 2,6-di-alkyl-phenolic proprionic ester derivatives.Bis-phenolic antioxidants may also be advantageously used in combinationwith the instant disclosure. Examples of ortho-coupled phenols include:2,2′-bis(4-heptyl-6-t-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol);and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenolsinclude for example 4, 4′-bis(2,6-di-t-butyl phenol) and4,4′-methylene-bis(2,6-di-t-butyl phenol).

Non-phenolic oxidation inhibitors which may be used include aromaticamine antioxidants and these may be used either as such or incombination with phenolics. Typical examples of non-phenolicantioxidants include: alkylated and non-alkylated aromatic amines suchas aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic,aromatic or substituted aromatic group, R⁹ is an aromatic or asubstituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)_(x)R¹²where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is ahigher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1or 2. The aliphatic group R⁸ may contain from 1 to 20 carbon atoms, andpreferably contains from 6 to 12 carbon atoms. The aliphatic group is asaturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic orsubstituted aromatic groups, and the aromatic group may be a fused ringaromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joinedtogether with other groups such as S.

Typical aromatic amines antioxidants have alkyl substituent groups of atleast 6 carbon atoms. Examples of aliphatic groups include hexyl,heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups willnot contain more than 14 carbon atoms. The general types of amineantioxidants useful in the present compositions include diphenylamines,phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenylphenylene diamines. Mixtures of two or more aromatic amines are alsouseful. Polymeric amine antioxidants can also be used. Particularexamples of aromatic amine antioxidants useful in the present disclosureinclude: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine;phenyl-alphanaphthylamine; and p-octylphenyl-alpha-naphthylamine.

Sulfurized alkyl phenols and alkali or alkaline earth metal saltsthereof also are useful antioxidants.

Preferred antioxidants include hindered phenols, arylamines. Theseantioxidants may be used individually by type or in combination with oneanother. Such additives may be used in an amount of 0.01 to 5 weightpercent, preferably 0.01 to 1.5 weight percent, more preferably zero toless than 1.5 weight percent, most preferably zero.

Pour Point Depressants (PPDs)

Conventional pour point depressants (also known as lube oil flowimprovers) may be added to the compositions of the present disclosure ifdesired. These pour point depressant may be added to lubricatingcompositions of the present disclosure to lower the minimum temperatureat which the fluid will flow or can be poured. Examples of suitable pourpoint depressants include polymethacrylates, polyacrylates,polyarylamides, condensation products of haloparaffin waxes and aromaticcompounds, vinyl carboxylate polymers, and terpolymers ofdialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers.U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655,479;2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pourpoint depressants and/or the preparation thereof. Such additives may beused in an amount of 0.01 to 5 weight percent, preferably 0.01 to 1.5weight percent.

Seal Compatibility Agents

Seal compatibility agents help to swell elastomeric seals by causing achemical reaction in the fluid or physical change in the elastomer.Suitable seal compatibility agents for lubricating oils include organicphosphates, aromatic esters, aromatic hydrocarbons, esters (butylbenzylphthalate, for example), and polybutenyl succinic anhydride. Suchadditives may be used in an amount of 0.01 to 3 weight percent,preferably 0.01 to 2 weight percent.

Anti-Foam Agents

Anti-foam agents may advantageously be added to lubricant compositions.These agents retard the formation of stable foams. Silicones and organicpolymers are typical anti-foam agents. For example, polysiloxanes, suchas silicon oil or polydimethyl siloxane, provide antifoam properties.Anti-foam agents are commercially available and may be used inconventional minor amounts along with other additives such asdemulsifiers; usually the amount of these additives combined is lessthan 1 weight percent and often less than 0.1 weight percent.

Friction Modifiers

A friction modifier is any material or materials that can alter thecoefficient of friction of a surface lubricated by any lubricant orfluid containing such material(s). Friction modifiers, also known asfriction reducers, or lubricity agents or oiliness agents, and othersuch agents that change the ability of base oils, formulated lubricantcompositions, or functional fluids, to modify the coefficient offriction of a lubricated surface may be effectively used in combinationwith the base oils or lubricant compositions of the present disclosureif desired. Friction modifiers that lower the coefficient of frictionare particularly advantageous in combination with the base oils and lubecompositions of this disclosure. Friction modifiers may includemetal-containing compounds or materials as well as ashless compounds ormaterials, or mixtures thereof. Metal-containing friction modifiers mayinclude metal salts or metalligand complexes where the metals mayinclude alkali, alkaline earth, or transition group metals. Suchmetal-containing friction modifiers may also have low-ashcharacteristics. Transition metals may include Mo, Sb, Sn, Fe, Cu, Zn,and others. Ligands may include hydrocarbyl derivative of alcohols,polyols, glycerols, partial ester glycerols, thiols, carboxylates,carbamates, thiocarbamates, dithiocarbamates, phosphates,thiophosphates, dithiophosphates, amides, imides, amines, thiazoles,thiadiazoles, dithiazoles, diazoles, triazoles, and other polarmolecular functional groups containing effective amounts of O, N, S, orP, individually or in combination. In particular, Mo-containingcompounds can be particularly effective such as for exampleMo-dithiocarbamates, Mo(DTC), Mo-dithiophosphates, Mo(DTP), Mo-amines,Mo (Am), Mo-alcoholates, Mo-alcohol-amides, etc. See U.S. Pat. Nos.5,824,627, 6,232,276, 6,153,564, 6,143,701, 6,110,878, 5,837,657,6,010,987, 5,906,968, 6,734,150, 6,730,638, 6,689,725, 6,569,820; WO99/66013; WO 99/47629; and WO 98/26030.

Ashless friction modifiers may also include lubricant materials thatcontain effective amounts of polar groups, for example,hydroxyl-containing hydrocarbyl base oils, glycerides, partialglycerides, glyceride derivatives, and the like. Polar groups infriction modifiers may include hydrocarbyl groups containing effectiveamounts of O, N, S, or P, individually or in combination. Other frictionmodifiers that may be particularly effective include, for example, salts(both ash-containing and ashless derivatives) of fatty acids, fattyalcohols, fatty amides, fatty esters, hydroxyl-containing carboxylates,and comparable synthetic long-chain hydrocarbyl acids, alcohols, amides,esters, hydroxy carboxylates, and the like. In some instances fattyorganic acids, fatty amines, and sulfurized fatty acids may be used assuitable friction modifiers.

Useful concentrations of friction modifiers may range from 0.01 weightpercent to 10-15 weight percent or more, often with a preferred range of0.1 weight percent to 5 weight percent. Concentrations ofmolybdenum-containing materials are often described in terms of Mo metalconcentration. Advantageous concentrations of Mo may range from 10 ppmto 3000 ppm or more, and often with a preferred range of 20-2000 ppm,and in some instances a more preferred range of 30-1000 ppm. Frictionmodifiers of all types may be used alone or in mixtures with thematerials of this disclosure. Often mixtures of two or more frictionmodifiers, or mixtures of friction modifier(s) with alternate surfaceactive material(s), are also desirable.

Viscosity Index Improvers

Viscosity index improvers (also known as VI improvers, viscositymodifiers, and viscosity improvers) can be included in the lubricantcompositions of this disclosure. Preferably, the method of thisdisclosure obtains improvements in fuel economy without sacrificingdurability by a reduction of high-temperature high-shear (HTHS)viscosity to a level lower than 2.6 cP through reduction or removal ofviscosity index improvers or modifiers.

Viscosity index improvers provide lubricants with high and lowtemperature operability. These additives impart shear stability atelevated temperatures and acceptable viscosity at low temperatures.

Suitable viscosity index improvers include high molecular weighthydrocarbons, polyesters and viscosity index improver dispersants thatfunction as both a viscosity index improver and a dispersant. Typicalmolecular weights of these polymers are between 10,000 to 1,500,000,more typically 20,000 to 1,200,000, and even more typically between50,000 and 1,000,000.

Examples of suitable viscosity index improvers are linear or star-shapedpolymers and copolymers of methacrylate, butadiene, olefins, oralkylated styrenes. Polyisobutylene is a commonly used viscosity indeximprover. Another suitable viscosity index improver is polymethacrylate(copolymers of various chain length alkyl methacrylates, for example),some formulations of which also serve as pour point depressants. Othersuitable viscosity index improvers include copolymers of ethylene andpropylene, hydrogenated block copolymers of styrene and isoprene, andpolyacrylates (copolymers of various chain length acrylates, forexample). Specific examples include styrene-isoprene orstyrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

Olefin copolymers, are commercially available from Chevron OroniteCompany LLC under the trade designation “PARATONE®” (such as “PARATONE®8921” and “PARATONE® 8941”); from Afton Chemical Corporation under thetrade designation “HiTEC®” (such as “HiTEC® 5850B”; and from TheLubrizol Corporation under the trade designation “Lubrizol® 7067C”.Polyisoprene polymers are commercially available from InfineumInternational Limited, e.g. under the trade designation “SV200”;diene-styrene copolymers are commercially available from InfineumInternational Limited, e.g. under the trade designation “SV 260”.

In an embodiment of this disclosure, the viscosity index improvers maybe used in an amount of less than 2.0 weight percent, preferably lessthan 1.0 weight percent, and more preferably less than 0.5 weightpercent, based on the total weight of the formulated oil or lubricatingengine oil.

In another embodiment of this disclosure, the viscosity index improversmay be used in an amount of from 0.0 to 2.0 weight percent, preferably0.0 to 1.0 weight percent, and more preferably 0.0 to 0.5 weightpercent, based on the total weight of the formulated oil or lubricatingengine oil.

When lubricating oil compositions contain one or more of the additivesdiscussed above, the additive(s) are blended into the composition in anamount sufficient for it to perform its intended function. Typicalamounts of such additives useful in the present disclosure are shown inTable 1 below.

It is noted that many of the additives are shipped from the additivemanufacturer as a concentrate, containing one or more additivestogether, with a certain amount of base oil diluent. Accordingly, theweight amounts in the table below, as well as other amounts mentioned inthis specification, are directed to the amount of active ingredient(that is the non-diluent portion of the ingredient). The weight percent(wt %) indicated below is based on the total weight of the lubricatingoil composition.

TABLE 1 Typical Amounts of Other Lubricating Oil Components ApproximateApproximate Compound wt % (Useful) wt % (Preferred) Dispersant  0.1-200.1-8  Friction Modifier 0.01-5  0.01-1.5 Antioxidant 0.1-5  0.1-1.5Pour Point Depressant 0.0-5 0.01-1.5 (PPD) Anti-foam Agent 0.001-3 0.001-0.15 Viscosity Index Improver 0.0-2 0.0-1  (solid polymer basis)

The foregoing additives are all commercially available materials. Theseadditives may be added independently but are usually precombined inpackages which can be obtained from suppliers of lubricant oiladditives. Additive packages with a variety of ingredients, proportionsand characteristics are available and selection of the appropriatepackage will take the requisite use of the ultimate composition intoaccount.

The following non-limiting examples are provided to illustrate thedisclosure.

EXAMPLES

Representative formulations are given in Table 2.

TABLE 2 Formulation Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. A Viscosity GradeComponent, wt % 0W 0W 0W 5W 0W-20 Salicylate and 2.73 2.73 3.52 * 2.73Sulfonate Detergent Mixture ZDDP 0.734 0.734 .75 * 0.734 Viscosity Index0.0 0.468 .12 0 0.702 Improver Other Additives Balance Balance Balance *Balance (dispersant, antioxidant, defoamant, PPD, seal swell agent,friction modifier) Base Oil 88.886 88.42 87.46 88.9 88.184 FormulatedOil 5.7 7.7 6.0 6.1 8.8 KV@100 C., cSt Formulation Comp. Comp. Comp. Ex.B Ex. C Ex. D Viscosity Grade Component, wt % 0W-20 5W-20 0W Salicylateand 3.52 * 2.73 Sulfonate Detergent Mixture ZDDP 0.75 * 0.734 Viscosityindex 0.561 0.315 0.78 improver Other Additives Balance * Balance(dispersant, antioxidant, defoamant, PPD, seal swell agent, frictionmodifier) Base oil 87.019 88.585 88.106 Formulated Oil 8.6 8.5 9.9KV@100 C., cSt * 10.8 weight % of Lubrizol 20018 commercially availableGF-4 additive package.

Among the features of the compositions of the disclosure is that therehas been demonstrated both unexpected combination of wear and fuelefficiency performance. For instance, fuel economy can be improved by atleast 0.4% as measured in the M111 FE engine test and while the wearperformance is improved relative to the comparison oils.

Performance evaluation of the formulations is given in Tables 3-11. Thefollowing engine tests were performed to measure wear and fuel economyof the engine oil lubricant composition of the present disclosure: TU3M(CEC L-038-94), M111FE (CEC L-054-96), Sequence IIIG (ASTM D7320),Sequence IVA (ASTM D6891), Sequence VID (ASTM D7589), OM646LA (CECL-099-08), Caterpillar 1M-PC (ASTM D6618) and Sequence VIII (ASTMD6709); all of which are incorporated herein by reference. HTHSviscosity was measured using ASTM D4683 which is incorporated herein byreference.

TABLE 3 Comp. Comp. Comp. Description Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. A Ex.B Ex. C Comp. Ex. D HTHS, 2.0 2.3 2.1 2.2 2.6 2.6 2.6 2.6 cP at 150° C.Viscosity Grade 0 W 0 W 0 W 5 W 0 W-20 0 W-20 5 W-20 0 W Engine TestParameter TU3M Valve Train Scuffing Wear Average cam 3.6 — 7.0 3.0 6.44.8 — — wear, μm Maximum 4.5 — 9.5 5.0 9.9 10.9  — — cam wear, μm Padrating 8.3 — 8.8 8.9 8.6 8.6 — — (average of 8), merits

The parameters listed in Table 3 above, and methods for determiningsame, are more fully described in CEC L-038-94.

TABLE 4 Comp. Comp. Comp. Comp. Description Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.A Ex. B Ex. C Ex. D HTHS, 2.0 2.3 2.1 2.2 2.6 2.6 2.6 2.6 cP at 150° C.Viscosity Grade 0 W 0 W 0 W 5 W 0 W-20 0 W-20 5 W-20 0 W Engine TestParameter M111FE Fuel Economy Fuel 3.77/4.01 3.91/3.69 — — — — —3.22/3.31 economy improvement vs. RL 191

The parameters listed in Table 4 above, and methods for determiningsame, are more fully described in CEC-L-054-96.

TABLE 5 Comp. Comp. Comp. Comp. Description Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.A Ex. B Ex. C Ex. D HTHS, 2.0 2.3 2.1 2.2 2.6 2.6 2.6 2.6 cP at 150° C.Viscosity Grade 0 W 0 W 0 W 5 W 0 W-20 0 W-20 5 W-20 0 W Engine TestParameter Sequence Wear and Oil IIIG Thickness Kinematic 52.5 — 51.4126.0  50.0 41.4 121.8  — viscosity increase at 40° C., % Average 6.43 —5.17 3.77 4.45 5.4 3.76 — weighted piston deposits, merits Hot stuckNone — None None None None None — rings Average cam 15.8 — 25.4 17.614.9 59 38.2 — and lifter wear, μm

The parameters listed in Table 5 above, and methods for determiningsame, are more fully described in ASTM D7320.

TABLE 6 Comp. Comp. Comp. Comp. Description Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.A Ex. B Ex. C Ex. D HTHS, 2.0 2.3 2.1 2.2 2.6 2.6 2.6 2.6 cP at 150° C.Viscosity Grade 0 W 0 W 0 W 5 W 0 W-20 0 W-20 5 W-20 0 W Engine TestParameter Sequence Valvetrain IVA Wear Average cam 11 — — — 12 — — —wear (7 point average), μm

The parameters listed in Table 6 above, and methods for determiningsame, are more fully described in ASTM D6891.

TABLE 7 Comp. Comp. Comp. Comp. Description Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.A Ex. B Ex. C Ex. D HTHS, 2.0 2.3 2.1 2.2 2.6 2.6 2.6 2.6 cP at 150° C.Viscosity Grade 0 W 0 W 0 W 5 W 0 W-20 0 W-20 5 W-20 0 W Engine TestParameter Sequence VID (modified Fuel test) Economy FEI, SUM 2.30 2.18 —— — — — 2.06 FEI 2 after 1.10 .85 — — — — — 0.99 100 hours aging, % FEI1 after 1.20 1.33 — — — — — 1.07 16 hours aging, %

The parameters listed in Table 7 above, and methods for determiningsame, are more fully described in ASTM D7589. In this case a slightlymodified version of ASTM D7589 was run; two additional samples weretaken during the test compared to the ASTM method.

TABLE 8 Comp. Comp. Comp. Comp. Description Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.A Ex. B Ex. C Ex. D HTHS, 2.0 2.3 2.1 2.2 2.6 2.6 2.6 2.6 cP at 150° C.Viscosity Grade 0 W 0 W 0 W 5 W 0 W-20 0 W-20 5 W-20 0 W Engine TestParameter OM646LA Wear — — — Main bearing 0.2 — — — 0.2 wear, μm Conrod0.0 0.2 bearing wear, μm Axial piston 11.0 8.6 ring wear, (1^(st) ring),μm Axial piston 0.4 0.8 ring wear, (2^(nd) ring), μm Axial piston 1.71.2 ring wear, (3^(rd) ring), μm Radial piston 9.5 6.8 ring wear,(1^(st) ring), μm Radial piston 2.4 7.9 ring wear, (2^(nd) ring), μmRadial piston 4.0 6.7 ring wear, (3^(rd) ring), μm Cam wear 67.4 89.7outlet (ave. max wear 8 cams), μm Cam wear 74.0 71.4 inlet (ave. maxwear 8 cams), μm Cylinder 2.8 2.9 wear (ave. 4 cylinders), μm Timingchain 0.2 0.2 elongation, % Bore 0.0 1.3 polishing (max.), % Tappet wear5.4 8.9 inlet Tappet wear 8.0 9.7 outlet Ring sticking none None (max.)Oil 6245 6185 consumption, g Viscosity 60.3 30.5 increase @100° C., %Soot, % 5.6 5.1 Piston 15.5 10.2 cleanliness, merits Average 9.03 9.2engine, sludge, merits

The parameters listed in Table 8 above, and methods for determiningsame, are more fully described in CEC L-099-08.

TABLE 9 Comp. Comp. Comp. Comp. Description Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.A Ex. B Ex. C Ex. D HTHS, 2.0 2.3 2.1 2.2 2.6 2.6 2.6 2.6 cP at 150° C.Viscosity Grade 0 W 0 W 0 W 5 W 0 W-20 0 W-20 5 W-20 0 W Engine TestParameter Caterpillar Diesel 1M- Deposit and PC Wear Top groove 37 — — —50 — — — fill, % Weighted 138.0 — — — 145.1 — — — total demerits Piston,ring None — — — None — — — and liner scuffing Piston ring none — — —none — — — sticking

The parameters listed in Table 9 above, and methods for determiningsame, are more fully described in ASTM D6618.

TABLE 10 Comp. Comp. Comp. Comp. Comp. Description Ex. 1 Ex. 2 Ex. 3 Ex.A Ex. A Ex. B Ex. C Ex. D HTHS, 2.0 2.3 2.1 2.2 2.6 2.6 2.6 2.6 cP at150° C. Viscosity Grade 0 W 0 W 0 W 0 W 0 W-20 0 W-205 W 5 W-20 0 WEngine Test Parameter Sequence Bearing VIII Corrosion Bearing 4.6 — 11.93.0 — — 21.6 — weight loss, mg 10 hour 5.69 — 6.13 6.12 — — 8.08 —stripped viscosity at 100° C., cSt

The parameters listed in Table 10 above, and methods for determiningsame, are more fully described in ASTM D6709.

As can be seen from the foregoing Tables, the composition of thedisclosure provided improved or equivalent antiwear properties whileproviding a substantial improvement in fuel economy when compared to theother oils identified. In the foregoing Tables, the blanks for enginetest properties indicate that no data was available for that particulartest.

What is claimed is:
 1. A method for improving fuel efficiency, while maintaining or improving wear protection, in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil having a HTHS viscosity of less than 2.6 cP at 150° C., said formulated oil having a composition comprising a lubricating oil base stock as a major component, and a zinc dialkyl dithio phosphate, a mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents; and a viscosity index improver, as minor components; wherein said composition contains less than 2 weight percent of the viscosity index improver, based on the total weight of the formulated oil; and wherein said composition is sufficient for the formulated oil to pass wear protection requirements of one or more engine tests selected from TU3M, Sequence IIIG, Sequence IVA and OM646LA.
 2. The method of claim 1 wherein the base oil comprises a Group I, Group II, Group III, Group IV or Group V base oil.
 3. The method of claim 1 wherein the lubricating oil base stock comprises a poly alpha olefin (PAO) or gas-to-liquid (GTL) oil base stock.
 4. The method of claim 1 wherein the alkali metal detergents and alkaline earth metal detergents are selected from metallic salicylates and sulfonates, and wherein the metallic salicylates and sulfonates are selected from calcium and magnesium.
 5. The method of claim 1 wherein the ZDDP is a secondary dialkyl dithio phosphate.
 6. The method of claim 1 wherein said composition contains less than 1 weight percent of the viscosity index improver, based on the total weight of the formulated oil.
 7. The method of claim 1 wherein the oil base stock is present in an amount of from 70 weight percent to 95 weight percent, the zinc dialkyl dithio phosphate (ZDDP) is present in an amount of from 0.4 weight percent to 1.2 weight percent, and the mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents, is present in an amount of from 1.0 weight percent to 6.0 weight percent, based on the total weight of the formulated oil.
 8. The method of claim 1 wherein said composition contains less than 0.5 weight percent of the viscosity index improver, based on the total weight of the formulated oil.
 9. The method of claim 1 wherein the formulated oil has a HTHS viscosity of less than 2.4 cP at 150° C.
 10. The method of claim 1 wherein the lubricating oil is a passenger vehicle engin oil (PVEO).
 11. A lubricating engine oil having a composition comprising a lubricating oil base stock as a major component, and a zinc dialkyl dithio phosphate, a mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents; and a viscosity index improver, as minor components; wherein said lubricating engine oil has a HTHS viscosity of less than 2.6 cP at 150° C.; wherein said composition contains less than 2 weight percent of the viscosity index improver, based on the total weight of the lubricating engine oil; and wherein said composition is sufficient for the lubricating engine oil to pass wear protection requirements of one or more engine tests selected from TU3M, Sequence IIIG, Sequence IVA and OM646LA.
 12. The lubricating engine oil of claim 11 wherein the oil base stock comprises a Group I, Group II Group III, Group IV or Group V base oil.
 13. The lubricating engine oil of claim 11 wherein the lubricating oil base stock comprises a poly alpha olefin (PAO) or gas-to-liquid (GTL) oil base stock.
 14. The lubricating engine oil of claim 11 wherein the alkali metal detergents and alkaline earth metal detergents are selected from metallic salicylates and sulfonates, and wherein the metallic salicylates and sulfonates are selected from calcium and magnesium.
 15. The lubricating engine oil of claim 11 wherein the ZDDP is a secondary dialkyl dithio phosphate.
 16. The lubricating engine oil of claim 11 wherein said composition contains less than 1 weight percent of the viscosity index improver, based on the total weight of the lubricating engine oil.
 17. The lubricating engine oil of claim 11 wherein the oil base stock is present in an amount of from 70 weight percent to 95 weight percent, the zinc dialkyl dithio phosphate (ZDDP) is present in an amount of from 0.4 weight percent to 1.2 weight percent, and the mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents, is present in an amount of from 1.0 weight percent to 6.0 weight percent, based on the total weight of the lubricating engine oil.
 18. The lubricating engine oil of claim 11 wherein said composition contains less than 0.5 weight percent of the viscosity index improver, based on the total weight of the lubricating engine oil.
 19. The lubricating engine oil of claim 11 which has a HTHS viscosity of less than 2.4 cP at 150° C.
 20. The lubricating engine oil of claim 11 comprising a passenger vehicle engine oil (PVEO). 